The Program of research is concerned with molecular mechanisms of neuronal survival and death in the aging brain and in Alzheimer's Disease (AD). We have proposed a wide spectrum of molecular genetic and cell biological approaches designed to gain new insights into the molecular pathogenesis of AD and, ultimately, to identify a gene involved in the etiology. Since amyloid accumulation is a significant neuropathologic manifestation of AD, we have cloned major portions of the A4 or beta- amyloid cDNA that was derived directly from AD postmortem brain mRNA. We now propose to use our cloned amyloid inserts, along with newly developed vectors, to prepare and analyze transfected cells and transgenic mice thus establishing models for amyloid overexpression. Because we were able to prepare cDNA libraries directly from AD postmortem brain mRNA, the libraries serve the second purpose of expediting the search for the chromosome 21 gene involved in the etiology of AD. These investigations will supplement the previously successful molecular genetic linker strategies of Program investigators. Amyloid gene expression in the AD brain and in the mouse and cell models will be analyzed by in situ hybridization, by monoclonal antibodies to amyloid precursor subdomains, and by investigations at the levels of transcription, translation and RNA metabolism. Thus, we propose to identify mechanisms relevant to amyloid accumulation and to document the pathological consequences of amyloid overexpression at the molecular and cellular levels. We further propose posttranslational modification and proteolysis studies of neuronal cytoskeletal-associated proteins that may have relevance to the metabolism of the amyloid precursor protein and which may illuminate aspects of neuronal plasticity. We shall also investigate a late-onset neurodegenerative disorder in mice that may have its origin in the lysosomal and non-lysosomal proteases. We propose to study fibroblast growth factors, known to affect neuronal survival and proliferation, in relation to the mature, aging and AD brain. Additional experiments will focus on synaptic macromolecules, including a specific growth associated protein, possibly related to deterioration of memory functions during normal human brain aging. Research carried out at the most basic level of molecular and cellular biology may ultimately provide the necessary information to develop a reliable diagnostic test for AD and offer meaningful therapeutic initiatives.